The invention lies in the mechanical arts and relates, more specifically, to an indexable cutting insert for turning, having a plurality of main cutting edges, adjacent main cutting edges, which enclose a corner angle with one another, being connected via a cutting corner which has two identical corner sections arranged symmetrically to the angle bisector.
In conventional indexable inserts, adjacent main cutting edges enclosing an angle with one another are generally connected to one another by a cutting corner having a single corner section in the form of a rounded corner portion or a finish cutting edge.
The term xe2x80x9crounded cornerxe2x80x9d portions is used in the context of indexable inserts to designate such corner designs in which the cutting corners are defined with arcs of a circle having radii which, in the most common indexable inserts, depending on the size of the indexable insert, lie within a range of between 0.4 and 2.4 mm. In indexable inserts with finish cutting edges, with which an improved surface quality is achieved, the cutting corners are formed as arcs of a circle whose radii, in approximation to a straight line, are many times larger than in the case of rounded corner portions.
In addition, indexable inserts in which each cutting corner consists of two identical corner sections are known for special applications. Such an indexable insert is described, for example, in published French patent application FR 1 260 357. In the indexable insert according to that specification, the adjacent main cutting edges are connected to one another by two equally long, approximately straight corner sections which enclose an obtuse angle with one another and are arranged symmetrically to the angle bisector. On the one hand, by such a configuration, the cutting corners of the indexable insert are reinforced. On the other hand, smoothing of the surface, which was previously machined by the main cutting edge and the leading corner section, is the to be achieved by the trailing second corner section. In that indexable insert, although each cutting corner consists of two identical corner sections, both adjacent corner sections always come into use simultaneously during a cutting operation and are subjected to wearing stress in one and the same work operation.
It is accordingly an object of the invention to provide an indexable cutting insert, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which has two identical cutting sections that are arranged symmetrically to the angle bisector and can be used independently of one another, and as a result of which better efficiency of the indexable insert is achieved.
With the foregoing and other objects in view there is provided, in accordance with the invention, an indexable insert for turning, comprising an insert body formed with a plurality of main cutting edges including adjacent main cutting edges enclosing a corner angle with one another and defining an angle bisector, a cutting corner connecting the main cutting edges, the cutting corner being formed with two mutually identical corner sections arranged symmetrically with regard to the angle bisector and defining an outer contour, and having a depression formed with respect to the adjacent outer contour directly at the angle bisector.
In accordance with an added feature of the invention, the corner sections are rounded corner portions.
In accordance with a concomitant feature of the invention, the corner sections are configured as finish cutting edges.
In other words, the objects of the invention are achieved in that the corner sections, in their region directly adjoining the angle bisector, have a depression with respect to the adjacent outer contours.
This special configuration can be realized in all the important shapes of indexable inserts, such as square, triangular, rectangular and rhombic shapes.
With the configuration according to the invention of the indexable insert, in each case adjacent corner sections are designed to be separate from one another. By suitable selection of the setting angle of the indexable inserts, this achieves the effect that, during a cutting operation with uniform cutting direction, in addition to the main cutting edge just in use, in each case only the adjoining corner section participates in the cutting, whereas the second corner section is completely released and is not subjected to any wear. The second unworn corner section, with its adjacent main cutting edge, does not come into use until the cutting direction is changed, e.g. from longitudinal turning to the left to longitudinal turning to the right, or from longitudinal turning to facing, whereas the corner section used beforehand, with its adjacent main cutting edge, is released. Depending on the geometry of the indexable insert and the type of change of the cutting direction, a change in the setting angle of the indexable insert may be necessary for this purpose.
In this way, at each indexable insert, the corner sections which can be used independently of one another are doubled and the efficiency is thus increased.
Thus, for example, in negative square indexable inserts, up to 16 cutting-edge regions which can be used independently of one another can be provided, whereby optimum utilization of the indexable inserts is achieved. Here, in each case a corner section with associated main cutting edge is to be regarded as the cutting-edge region.
Since the cutting-edge region which is in use during the cutting does not extend directly up to the angle bisector between the two corner sections, it is possible to bring the central seating surface of the indexable inserts in the region of each angle bisector directly up to the outer edges of the indexable insert. This results in optimum seating of the indexable insert without the cutting insert tilting up even under very high loading.
Of course, the advantages of the indexable insert according to the invention are only completely effective when the indexable insert is used in cutting operations having different cutting directions, which, however, is the case in many machining operations.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an indexable cutting insert for turning, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.